form_fieldtype(3x) — Linux manual page


form_fieldtype(3X)                                    form_fieldtype(3X)

NAME         top

       form_fieldtype - define validation-field types

SYNOPSIS         top

       #include <form.h>

       FIELDTYPE *new_fieldtype(
           bool (* const field_check)(FIELD *, const void *),
           bool (* const char_check)(int, const void *));
       int free_fieldtype(FIELDTYPE *fieldtype);

       int set_fieldtype_arg(
           FIELDTYPE *fieldtype,
           void *(* const make_arg)(va_list *),
           void *(* const copy_arg)(const void *),
           void  (* const free_arg)(void *));
       int set_fieldtype_choice(
           FIELDTYPE *fieldtype,
           bool (* const next_choice)(FIELD *, const void *),
           bool (* const prev_choice)(FIELD *, const void *));

       FIELDTYPE *link_fieldtype(FIELDTYPE *type1,
                                 FIELDTYPE *type2);

DESCRIPTION         top

       The function new_fieldtype creates a new field type usable for
       data validation.  Its parameters are function pointers:

            This function checks the validity of an entered data string
            whenever the user attempts to leave a field.  It has two

            •   The (FIELD *) argument is passed in so the validation
                predicate can see the field's buffer, sizes and other

            •   The second argument is an argument-block structure,
                about which more below.

            This function validates input characters as they are
            entered.  The form library passes it the character to be
            checked and a pointer to an argument-block structure.

       The free_fieldtype function frees the space allocated for a given
       validation type by new_fieldtype.

       The function set_fieldtype_arg associates three storage-
       management functions with a field type:

            This function is automatically applied to the list of
            arguments you give set_field_type when attaching validation
            to a field.  It stores the arguments in an allocated
            argument-block object which is used when validating input.

            This function may be used by applications to copy argument-

            Frees an argument-block structure.

       You must supply the make_arg function.  The other two are
       optional: you may supply NULL for them.  In this case, the form
       library assumes that make_arg does not allocate memory but simply
       loads the argument into a single scalar value.

       The form driver requests REQ_NEXT_CHOICE and REQ_PREV_CHOICE
       assume that the possible values of a field form an ordered set,
       and provide the forms user with a way to move through the set.

       The set_fieldtype_choice function allows forms programmers to
       define successor and predecessor functions for the field type.
       These functions take the field pointer and an argument-block
       structure as arguments.

       The function link_fieldtype creates a new field type from the two
       given types.  They are connected by an logical 'OR'.

RETURN VALUE         top

       The pointer-valued routines return NULL on error.  They set errno
       according to their success:

       E_OK The routine succeeded.

            Routine detected an incorrect or out-of-range argument.

            System error occurred, e.g., malloc failure.

       The integer-valued routines return one of the following codes on

       E_OK The routine succeeded.

            Routine detected an incorrect or out-of-range argument.

            The field is already connected to a form.

            The field is the current field.

            System error occurred (see errno(3)).

SEE ALSO         top

       curses(3X), form(3X), form_field_validation(3X).

NOTES         top

       The header file <form.h> automatically includes the header file

PORTABILITY         top

       These routines emulate the System V forms library.  They were not
       supported on Version 7 or BSD versions.

AUTHORS         top

       Juergen Pfeifer.  Manual pages and adaptation for new curses by
       Eric S. Raymond.

COLOPHON         top

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